Horticulture

Bagworms

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One common horticultural pest our office receives questions on is bagworms. Bagworms feed on the foliage of a wide variety of trees and shrubs, but are of most concern for evergreens, especially junipers. Bagworms overwinter as eggs in their bags which are attached to tree branches. The eggs hatch in mid-May to early June. As bagworms grow, leaf fragments are added to bags which often grow to 2 inches in length by the end of the summer. The earliest signs of bagworm injury in evergreens are brown or stressed needles at the tips of branches. Heavy infestations  of older bagworms may completely defoliate a tree or shrub and if severe enough can kill the tree or shrub. Less severe injury will slow growth and stunt plants.

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To control bagworms on small trees or small infestations, remove the bags by pulling them off the branches and immersing them in soapy water. If you place the bags next to the tree, the larvae might return to the host plants. If you have bagworms in a windbreak or large tree, insecticides are most effective when applied during early bagworm development. For early season damage, insecticides from mid to late June when bags are less than ½ inch in length are effective. By late August, chemical control is no longer effective as the bagworms have ceased feeding and are enclosed within their bags.

Reduced-risk insecticides to use contain Bacillus thuringiensis (Bt) and insecticidal soaps are quite effective on young bagworm larvae but may require repeated applications. Additional insecticide options for bagworms include: acephate, bifenthrin, carbaryl, cyfluthrin, malathion or others. As always, be sure to read and follow all label instructions and use all insecticides with caution to avoid exposure to humans, pets, wildlife and other non-target organisms.

For more information, check out Nebraska Extension’s NebGuide on bagworms which can be accessed online through extension.unl.edu websiteor in our office.

Horticulture

Lawn & Tree Tips

Nebraska Extension offers excellent resources on varying horticultural topics. One of those sources is an online, Horticultural Update newsletter at http://hortupdate.unl.edu/. The most recent articles had lots of great information, so I’ve highlighted two of those in this week’s column.

First, I’m sure you’ve noticed this has been perfect condition for weeds to take over landscapes and gardens in a hurry. The wet weather has also encouraged an increase in broadleaf weeds in turf. Control involves good management to promote a dense, vigorous turf that competes with weeds. Use a tall mowing height of three inches to reduce seed germination and to shade out weed seedlings.

September is the best month to control broadleaf perennial weeds with herbicides. If herbicides are used during summer, read label directions for temperature ranges within which to apply. Hot temperatures will increase damage potential to nontarget plants. Whenever used, spot applications are best as they result in the smallest amount of herbicide being used; saving money and protecting the environment. Read and follow label directions. Labels are the law and herbicides should not be used outside of recommended temperature ranges.

Another thing to watch for is bagworms hatching on evergreens trees. Monitor evergreens for young bagworms. At this time of year, they can be as small as one-fourth inch long. Bagworms are small, brown, triangular-shaped and covered with needles for camouflage.  At this size is the time when products like Bacillus thuringiensis will be most effective in controlling bagworms.

Finally, mosquitoes are awful this year! Public Health Solutions has brought us some mosquito dunks, which can reduce mosquito number by putting them in landscape ponds, livestock tanks and other sources of standing water. Standing water areas can be treated with a biological larvicide. Bacillus thruingiensis israelensis (Bti) or Bacillus sphaericus (Bs) are naturally occurring soil bacterium that control mosquito larvae by disrupting the gut receptors and causes the larvae to stop eating anddie. Biological larvicides are safe to use in water of livestock troughs. Stop in to pick up your free sample of mosquito dunk!

(Source: NE Extension HortUpdate, 2015)